1. Field of the Invention
This invention relates to a method, and to apparatus for carrying out the method, for separating particles suspended in a fluid carrier according to the magnetic susceptibilities of the particles. While not so limited, the invention has particular application to the separation in a fluid medium of particles 100 mesh (147 microns) or less in size.
2. The Prior Art
As is well known, the differential responses of materials to magnetic forces may be used as a basis for separating the materials in accordance with their particular magnetic susceptibilities. One device embodying this principle is described in U.S. Pat. No. 2,056,426, issued on Oct. 6, 1936 to S. G. Frantz. Magnetic separators constructed in accordance with the Frantz patent are manufactured and sold by S. G. Frantz Company, Trenton, New Jersey, assignee of the present application, under the trademark ISODYNAMIC. Unlike other separators, the Frantz ISODYNAMIC separator employs an isodynamic magnetic field, i.e., a field which exerts a substantially constant force on a particle of given susceptibility regardless of the position of the particle within the field, and as a consequence is capable of making positive and quite fine separations. This sensitivity, which enables delicate separations of many materials throughout the entire spectrum of susceptibilities down through the diamagnetic, makes the Frantz ISODYNAMIC separator useful in a wide variety of research and industrial applications and has led to its worldwide adoption by university, government and industrial laboratories and by basic research institutions.
The operating range of the Frantz ISODYNAMIC separator, however, has heretofore been limited almost entirely to dry flowable materials having a particle size greater than about 100 to 200 mesh (147 to 74 microns). Consequently, in the many instances where because of the nature of the material or for other reasons it is desirable or advantageous to work with wet or other fluid suspended samples and/or to effect separation of materials of finer particle sizes, prior art magnetic separating apparatus and techniques have been unavailable. It is the object of the present invention to fulfill these and other requirements of the prior art.